In general, a jet loom has a main nozzle for spouting, i.e., directing, projecting or ejecting, a weft into warp openings, and a reed which has a plurality of reed pieces arranged between warps, in order to beat a weft, inserted in the warp openings, in a cloth fell. As shown in FIG. 13, a weft insertion device for a jet loom has an open type guide openings 32, and is formed in the front faces of the reed pieces 31. The walls of the guide openings 32 form a passage S for weft insertion.
Japanese Examined Patent Publication No. 59-26688 and Japanese Unexamined Patent Publication No. 1-314753 disclose weft insertion devices, in which the open type guide opening 32 has its top wall surface 32a, side wall surface 32b and bottom wall surface 32c inclined toward the weft passage S in the weft inserting direction, in order to improve the speed of a weft flying through the weft passage.
In the weft insertion device disclosed in the Japanese Examined Patent Publication No. 59-26688, the inclination angles of the individual wall surfaces 32a, 32b and 32c of each guide opening are increased in order to increase the flow speed of jet air in the weft passage, thereby increasing the weft flying speed. The increase in the inclination angle of the side wall surface 32b increases the amount of air leak from the guide openings, which cause a flying trouble, such as the distal end of the weft flying out of the weft passage. However, this design increases the weft flying speed.
In the weft insertion device disclosed in the Japanese Unexamined Patent Publication No. 1-314753, the inclination angle of the top wall surface 32a is greater than that of the side wall surface 32b. Further, a jet air from a plurality of sub-nozzles arranged along the weft passage S is directed toward the top wall surfaces 32a and the side wall surfaces 32b of the individual guide openings. This setting of the inclination angles of the top wall surface 32a and side wall surface 32b will suppress air leakage from the guide openings.
In the weft insertion devices disclosed in both publications, however, the inclination angles of the wall surfaces 32a, 32b and 32c of each guide opening are set evenly from the weft insertion inlet end to the outlet end thereof. This angle setting is not an effective means to improve the weft flying speed, while preventing the weft from flying away from the weft passage.
The flow rate of air upstream the weft passage becomes the sum of the flow rate of jet air from the main nozzle and that of jet air from the individual sub-nozzles. Therefore, the flow rate of the air moving upstream, becomes about twice that of the air moving downstream, which is less affected by the jet stream from the main nozzle. Due to this flow ratio, the amount of the air leak, toward the opening side of the guide openings of those reed pieces located upstream of the weft passage, is greater than that of the air leak located downstream.
If the inclination angle of all the side wall surfaces is smaller in view of the air leak toward the opening side of the upstream guide openings, it is possible to prevent the weft from flying away from the weft passage, but it is difficult to improve the flying speed. If the inclination angle of all the side wall surfaces is greater in accordance with the maximum allowable air leak toward the opening side of the downstream guide openings, on the other hand, it is possible to improve the flying speed, but it is not possible to effectively prevent the weft from flying away from the weft passage. Even if the inclination angles of the top wall surface 32a and the side wall surface 32b are set different from each other as described above, it will be difficult to prevent the weft from flying away from the weft passage, as well as to improve the flying speed.
It is therefore an object of the present invention to provide an improved weft insertion device in a jet loom using an improved reed, including open type guide openings. The improved device can effectively prevent the flying trouble while improving the flying speed of a weft. It is also another object of this invention to provide a reed for the weft insertion device and a method of producing the reed.